There is no single definition of a cognate; however, the benefits of cognates in learning a second language (L2) are widely accepted in SLA. Daulton introduces two views of cognates: diachronic and synchronic. In the diachronic view, cognates are defined as words with the same meaning and a similar form in two languages that belong to the same language family (e.g., English and Spanish). In the synchronic view, cognates are defined as words that share recognizable similarities between two modern languages. Although Japanese and English do not share any cognates in the diachronic view, Japanese contains a number of words borrowed from English. The borrowed words are phonologically similar and semantically identical to their English counterparts (e.g., Japanese ekonomii vs. English economy). Many English loanwords in Japanese are academic and high-frequency words; therefore, by adopting the synchronic view of cognates, Daulton argues that Japanese has a large built-in English lexicon. Additionally, he claims that the advantages of cognates in learning a L2 can be explored in Japanese first language (L1) learners’ acquisition of English. For example, similarities in word forms enable L2 learners to easily identify and infer meaning using L1 lexical knowledge, which is not available for noncognates. Cognates can also enhance L2 reading and listening comprehension.

Despite the optimal features, Daulton admits shortcomings of directly applying lexical knowledge of loanwords to learning English vocabulary. First, phonological modification happens when English words are adopted into Japanese; therefore, pronunciation practice is necessary. Second, loanwords do not carry inflectional and derivational morphological information; therefore, the practice of English affixes should be encouraged. Finally, truncation or word-shortening is frequently observed for loanwords; therefore, it is necessary to explicitly inform L2 learners of the forms on which the loanwords are based.

The fact that Japanese has many English loanwords can benefit L2 learners in acquiring English vocabulary by transferring the built-in, lexical knowledge of the vocabulary. The only concern is that Japanese also contains loanwords from other languages (e.g., German, Portuguese, and French), so it is important to distinguish the source of loanwords. This book provides many interesting topics for SLA and psycholinguistics research, which include how L2 learners of English and L2 learners of Japanese process loanwords, how the words are stored and retrieved in the lexicon, and how pronunciation and reading comprehension are affected.